Update README.md

Author: jeantimex

README.md

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 # How to Implement Collapsible Table Section in iOS
 
-[![Language](https://img.shields.io/badge/swift-3.0-brightgreen.svg?style=flat)]()
+[![Language](https://img.shields.io/badge/swift-4.2-brightgreen.svg?style=flat)]()
 
 A simple iOS swift project demonstrates how to implement collapsible table section programmatically, that is no main storyboard, no XIB, no need to register nib, just pure Swift!